Ask ten installers which solar panel is best and you will hear four brands and a lot of loyalty. The more useful answer is that the best panel is the one that suits your roof, meets the rules for the STC discount, comes with a warranty from a company that will still exist in 20 years, and is fitted by someone who will answer the phone in year eight. Brand lists date fast, and rankings are a snapshot, so this guide sets out how to judge a panel rather than naming winners.
Panels are also less of the story than people think. A good installer, a good inverter and a sensible design usually matter more to your bill than the difference between two decent panels. Keep that in proportion as you read the specifications. For what the whole system costs, see how much solar panels cost in Australia.
Start with the rules: approved panels
For a system to create STCs, the panels must meet the scheme’s requirements. In practice, that means they should be on the Clean Energy Council’s approved products list and meet the relevant Australian standards. The Clean Energy Regulator runs the Solar Panel Validation Initiative to catch claims for unapproved panels. If a quote includes a panel that is not on the list, the system may not create certificates, and the discount on your quote may disappear.
Ask your installer to confirm that the exact model number is approved, not just the brand. Keep that confirmation with your paperwork.
The specifications that matter
Here is what each key figure means and what is typical today. Ranges are indicative. Check the datasheet for the actual panel.
| Spec | What it tells you | Typical range |
|---|---|---|
| Efficiency | Power per square metre of panel | About 20 to 23% |
| Power rating | Watts per panel | About 400 to 450 W |
| Temperature coefficient | How much output falls as panels heat up | Lower magnitude is better; around -0.30 to -0.40% per degree C |
| Degradation | Yearly output loss | Often around 0.4 to 0.55% a year |
| Product warranty | Covers defects | 10 to 25 years |
| Performance warranty | Guaranteed output | 25 to 30 years |
Efficiency
Higher efficiency means more watts from each panel. It matters on small or shaded roofs where area is the limit. On a big, clear roof you can reach the same system size with cheaper, slightly lower-efficiency panels, and nothing is lost.
Temperature coefficient
Australian roofs get hot, and panels lose output as they do. A panel with a better temperature coefficient gives up less on a 40 degree day. The difference between two good panels is small, but across a long hot summer it adds up, and it is a fair tiebreaker.
Degradation and performance warranty
All panels lose some output over time. A panel that degrades at 0.4 percent a year keeps about 90 percent of its output after 25 years, while one at 0.55 percent keeps about 87 percent. Over a long life, that is a modest but real difference.
Warranty, and who stands behind it
Read both warranties, product and performance. Then ask who honours them in Australia. A 25-year warranty from a company with no local presence is worth much less than a 15-year warranty from one with local service. Ask how a claim works: who pays for removal and reinstallation, and whether the installer or manufacturer handles it.
Cell technology, briefly
Most new panels sold in Australia use modern cell designs such as TOPCon, which have improved efficiency and temperature behaviour compared with older designs. You do not need to master the engineering. Ask the installer what technology is in the panel and why they chose it, and check that the panel’s datasheet figures sit within the ranges above.
A worked comparison
Two quotes for 6.6 kW (illustrative):
| Panel A | Panel B | |
|---|---|---|
| Panels | 15 x 440 W | 16 x 415 W |
| Efficiency | 22.5% | 21.0% |
| Temperature coefficient | -0.29% | -0.35% |
| Product warranty | 25 years | 12 years |
| Price after STC | $6,300 | $5,400 |
Panel A costs $900 more. Over a life of 25 years, the better temperature behaviour and slower degradation might add a few percent to output, worth perhaps $30 to $60 a year at typical tariffs, or roughly $750 to $1,500 over the system’s life. The longer product warranty is worth something extra if a defect appears. Whether $900 is worth it depends on your roof, your plans and how long you will stay in the home. For many households, B is a perfectly sensible choice, and for others A is. There is no universal answer.
From the desk: Ask the installer which panel they would put on their own roof and why. A good installer will answer in specifics: the warranty process they have used, failure rates they have seen, how often they have had to deal with the manufacturer. An answer based entirely on the margin they make is worth noting.
The inverter and the installer
Panels last 25 years. Inverters often do not. Most inverters need replacing at least once during the life of the system, and many of the faults homeowners experience trace back to the inverter or installation, not the panels. Give the inverter as much attention as the panel: brand, warranty length, local support and battery readiness. If you might add a battery later, see our battery pages for how the federal program works and ask for an inverter that suits.
The installer matters most. Check accreditation, licensing, insurance and workmanship warranty, and read recent reviews. The best panel poorly installed will underperform and may void parts of its warranty.
Does the STC discount depend on the panel?
Only in one respect: the panel must be eligible. The number of certificates depends on the system size, your zone and the deeming period, not on which approved panel you pick. For 2026 installs the deeming period is five years. See deeming period and zone ratings for the calculation.
About rankings
You will find plenty of “best panels” lists online. Treat them cautiously. Some are sponsored, many reflect a snapshot of lab or field tests, and the market moves fast. If you want comparisons of specific brands or products, look for independent testing and long-term reliability data. This guide deliberately sticks to how to choose.
What to do next
- Ask each installer for the exact panel model, datasheet and warranty documents
- Confirm the model is on the approved list
- Compare quotes on a like-for-like basis using solar panel prices in Australia for 2026
- Browse our resources and STC trading overview to see how the discount on your quote becomes cash for the installer